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staging: usbip: prevent possible buffer overflow reading port records

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To avoid buffer overflow while reading a corrupted or possibly
modified port file we validate the length of each part of the port
record to ensure it doesn't exceed the length of the destination
buffer.

https://bugzilla.kernel.org/show_bug.cgi?id=69931

Signed-off-by: Mark Asselstine <asselsm@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mark Asselstine 2014-02-12 21:47:56 -05:00 committed by Greg Kroah-Hartman
parent ab09248c99
commit a37d70eb65
1 changed files with 46 additions and 5 deletions
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51
drivers/staging/usbip/userspace/libsrc/vhci_driver.c
View file

@ -339,27 +339,67 @@ static int get_hc_busid(char *sysfs_mntpath, char *hc_busid)
return -1;
}
static int read_record(int rhport, char *host, char *port, char *busid)
/*
* Read the given port's record.
*
* To avoid buffer overflow we will read the entire line and
* validate each part's size. The initial buffer is padded by 4 to
* accommodate the 2 spaces, 1 newline and an additional character
* which is needed to properly validate the 3rd part without it being
* truncated to an acceptable length.
*/
static int read_record(int rhport, char *host, unsigned long host_len,
char *port, unsigned long port_len, char *busid)
{
int part;
FILE *file;
char path[PATH_MAX+1];
char *buffer, *start, *end;
char delim[] = {' ', ' ', '\n'};
int max_len[] = {(int)host_len, (int)port_len, SYSFS_BUS_ID_SIZE};
size_t buffer_len = host_len + port_len + SYSFS_BUS_ID_SIZE + 4;
buffer = malloc(buffer_len);
if (!buffer)
return -1;
snprintf(path, PATH_MAX, VHCI_STATE_PATH"/port%d", rhport);
file = fopen(path, "r");
if (!file) {
err("fopen");
free(buffer);
return -1;
}
if (fscanf(file, "%s %s %s\n", host, port, busid) != 3) {
err("fscanf");
if (fgets(buffer, buffer_len, file) == NULL) {
err("fgets");
free(buffer);
fclose(file);
return -1;
}
fclose(file);
/* validate the length of each of the 3 parts */
start = buffer;
for (part = 0; part < 3; part++) {
end = strchr(start, delim[part]);
if (end == NULL || (end - start) > max_len[part]) {
free(buffer);
return -1;
}
start = end + 1;
}
if (sscanf(buffer, "%s %s %s\n", host, port, busid) != 3) {
err("sscanf");
free(buffer);
return -1;
}
free(buffer);
return 0;
}
@ -573,7 +613,8 @@ int usbip_vhci_imported_device_dump(struct usbip_imported_device *idev)
if (idev->status == VDEV_ST_NULL || idev->status == VDEV_ST_NOTASSIGNED)
return 0;
ret = read_record(idev->port, host, serv, remote_busid);
ret = read_record(idev->port, host, sizeof(host), serv, sizeof(serv),
remote_busid);
if (ret) {
err("read_record");
read_record_error = 1;